cntchr function

cntchr.c

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

size_t cntchr(const char *str, char value) {
    size_t count = 0;
    while ((str = strchr(str, value)) != NULL) {
        ++str;
        ++count;
    }
    return count;
}

size_t cntnchr(const char *str, char value, size_t num) {
    size_t count = 0;
    const char *pos;
    while ((pos = memchr(str, value, num)) != NULL) {
        num -= (pos - str);
        str = pos + 1;
        ++count;
    }
    return count;
}

#define X(_str, chr) printf(_str " contains %c %zu times\n", chr, cntchr(_str, chr))
#define XN(_str, chr) printf(_str " contains %c %zu times\n", chr, cntnchr(_str, chr, strlen(_str)))

int main() {
    X("nata", 'a');
    X("Zzattackzaazzzz", 'z');

    XN("nata", 'a');
    XN("Zzattackzaazzzz", 'z');

    return 0;
}